1. Field of the Invention:
The present invention relates generally to materials used in welding, and particularly to the preparation of welding inserts, or spacers that are utilized between surfaces to be joined by the welding method.
2. Description of the Prior Art:
In general, consumable inserts are well known and have for many years been utilized in complex welding situations, such as in the welding of pipes or tubular bore products, where because of their dimension, access to the weld point is limited. The specifications for consumable inserts are well known and have been stated in numerous industry publications, among them the American Welding Society specification AWS A5.30-79, entitled "Specification for Consumable Inserts", published by the American Welding Society, Incorporated, Miami, Florida, the entirety of which is incorporated herein by reference. As stated therein, consumable inserts are utilized where welding is conducted from one side of the junction of two metal surfaces, either for the maintenance of consistent high quality welds, where welding conditions are less then optimum, or in the instance where it is necessary to minimize obstructions within the inside of the tubular bored joint.
As a review of the above mentioned publication will reveal, most consumable inserts are ring-like in shape, and are thus generally intended for use in the formation of pipe or tubular bored joints. Various well known cross-sectional configurations are utilized, and are recited in the American Welding Society (AWS) publication, that may be chosen in accordance with the specific contour of the surfaces to be joined. For example, a common cross-sectional configuration is identified as the "T" shape, and such shape is illustrated infra. herein in FIG. 1. Likewise, another common shape comprises the "J" shape illustrated herein as well. Each shape is suited for specific application, and all shapes must be prepared to exacting tolerances on the order of up to about 0.005" or less.
The criticality of the dimensional requirements for consumable inserts is made all the more important, when it is considered the materials out of which these inserts are manufactured are all relatively hard metals, such as chromium molybdenum steels, austenitic chromium nickel steels, nickel alloys, including copper-nickel alloys and mild steel. Generally, consumable inserts have been prepared by machining to the desired tolerance, as the materials out of which these inserts are manufactured are of a hardness that has discouraged cold-working techniques. Also, the raw wire for conversion to the consumable insert must meet certain hardness standards, known as Rockwell B hardness, and in particular, must conform to a rating of from 60 to 80.
Thus, the extreme hardness and low workability of the materials required for the manufacture of consumable inserts, together with the exacting tolerance to which such inserts must be manufactured, and the tensile strength and Rockwell hardness values that the resulting products must possess to meet known standards, have all militated against the employment of any metal forming techniques, whether conducted at room temperature or at elevated temperatures. A particular drawback and concern, results from the known tendency of metal undergoing forming to work harden. As consumable inserts should reside within specific ranges of hardness, i.e. between approximately 72 to 100,000 psi tensile strength, earlier attempts to prepare such spacers by forming techniques were discouraged when it was found that the tensile strength of the final product resided outside the accepted range for the particular product, affording an unsuitable bend range for forming the insert ring; thus rendering the material unworkable.
As noted earlier, therefore, the technique of machining has been generally utilized in the industry to prepare consumable inserts. While this technique results in the preparetion of generally acceptable products, it, too possesses many drawbacks. Such drawbacks include the inefficiency in metal removal and retrieval, associated with the presence of burrs on the edges of the rings, and unevenness in the surfaces that directly abut the surfaces of the articles to be joined. The unevenness in the formed surfaces, known as "lands" leads to gaps between the joined surfaces that promotes the development of the undesired cracks and other imperfections in the welded joint, which imperfections affect the fusibility and soundness of the weld, and generally cause the weld to fail.
A need therefore exists to develop a technique for the manufacture of consumable inserts, that is more efficient and results in the preparation of a reliable product having the desired tensile strength and dimensional stability necessary for this product.